VBUS voltage monitoring is mandated by USB specification for self-powered devices. This implementation maps selected GPIO to bvalid signal of USB-OTG peripheral. Closes https://github.com/espressif/esp-idf/issues/7747
1. Renamed SOC_USB_SUPPORTED to SOC_USB_OTG_SUPPORTED for the reason of another USB related peripheral: USB_JTAG_SERIAL 2. correct related document